The present invention is generally related to capacitance sensors for determining the presence of an object and, more particularly, to a capacitance sensor having a non-conductive compressible element between flexible conductors for determining the presence of an object.
Various types of sensors are used to determine the presence, size, and/or position of an object such as a human body part. For example, in the automotive industry, sensors are used for pinch sensing at electrically operated doors, windows, hatches, decks, hoods, lids, and the like and for seat occupant sensing.
A pinch sensor detects the presence of an object such as a finger, hand, and the like being pinched by a closed opening such as a window. In operation, the pinch sensor generates a pinch signal in response to an object being pinched by the window. In response to the pinch signal, a controller controls the window to reverse direction to prevent further pinching and allow the object to be removed from the opening. A seat occupant sensor generates an occupant signal indicative of characteristics of an object such as a human occupant sitting on a seat. A controller uses the occupant signal to control various systems such as an air bag system as a function of the occupant""s characteristics (adult or child) sitting on the seat.
Motor current sensors, infrared beam sensors, and continuous switch sensors have been used for pinch sensing. A problem with motor current sensors and infrared beam sensors is that they can be fooled into causing an electrically closed opening to remain open due to changing mechanical and environmental conditions. A problem with continuous switch sensors is that they do not provide any lag time between switch activation and a pinch of an object. Thus, what is needed is a pinch sensor that is reliable in view of changing mechanical and environmental conditions and that provides a lag time to prevent a pinch of the object.
Fiber-optic sensors, ultrasonic sensors, electromagnetic sensors, piezometric sensors, and switch matrix sensors have been used for seat occupant sensing. A problem with these types of seat occupant sensors is that they are complex and costly. Thus, what is needed is a seat occupant sensor that is simple and cost efficient.
Accordingly, it is an object of the present invention to provide a capacitance sensor having a non-conductive compressible element between flexible conductors for determining the presence of an object.
It is another object of the present invention to provide a pinch capacitance sensor having a non-conductive compressible element between flexible conductors for determining the presence of an object about to be pinched by a closed opening.
It is a further object of the present invention to provide a seat occupant capacitance sensor having a non-conductive compressible element between flexible conductors for determining seat occupant characteristics such as presence, size, position, and type of the seat occupant.
It is still another object of the present invention to provide a seat occupant capacitance sensor having a non-conductive compressible element between flexible conductors for determining whether a seat object is an animate or inanimate object.
In carrying out the above objects and other objects, the present invention provides a sensor for determining the presence of an object. The sensor includes first and second flexible conductor elements separated by a separation distance and having a capacitance dependent on the separation distance. A non-conductive compressible element is interposed between the first and second flexible conductor elements. The non-conductive compressible element compresses in response to an object applying a force to at least one of the first and second flexible conductor elements such that the separation distance between the first and second flexible conductor elements decreases. The capacitance of the first and second flexible conductor elements changes in response to the separation distance between the first and second flexible conductor elements decreasing.
The sensor may include a controller for monitoring the capacitance of the first and second flexible conductor elements. The controller determines the presence of an object applying a force to at least one of the first and second flexible conductor elements in response to the capacitance of the first and second flexible conductor elements changing.
The controller, which may include a microprocessor, may be operable for generating an offset signal to bias the capacitance between the first and second flexible conductor elements. The controller may be operable for executing filtering software to monitor the capacitance between the first and second flexible conductor elements. The controller may be operable for executing an adaptive threshold detection algorithm to monitor the capacitance between the first and second flexible conductor elements.
The first flexible conductor element may be a center core with the second flexible conductor element coaxially surrounding the non-conductive compressible element and the first flexible conductor element. The second flexible conductor element is preferably electrically grounded. An elastomeric overcoat may coaxially surround the second flexible conductor element.
The sensor may further include a non-conductive compressible core. In this case, the first flexible conductor element coaxially surrounds the non-conductive compressible core, the non-conductive compressible element coaxially surrounds the first flexible conductor element, and the second flexible conductor element coaxially surrounds the non-conductive compressible element.
The sensor may further include a third flexible conductor element. In this case, the second and third flexible conductor elements are electrically grounded and surround at least a portion of the first flexible conductor element. The non-conductive compressible element is interposed between the first, second, and third flexible conductor elements such that the first and second flexible conductor elements are separated by a first separation distance and have a first capacitance dependent on the first separation distance, and the first and third flexible conductor elements are separated by a second separation distance and have a second capacitance dependent on the second separation distance. The first and second capacitances change in response to the first and second separation distances decreasing when an object applies a force to at least one of the second and third flexible conductor elements.
The non-conductive compressible element may include a cell foam, at least one of the first and second flexible conductors elements may include a braided electrically conductive wire or an electrically conductive plate.
Further, in carrying out the above objects and other objects, the present invention provides a pinch sensor system for determining the presence of an object within an opening defined by a closed opening device. The pinch sensor system includes a compressible capacitance pinch sensor fixedly positioned adjacent a closed opening device. The compressible capacitance pinch sensor has first and second flexible conductor elements separated by a separation distance. The first and second flexible conductor elements have a capacitance dependent on the separation distance. The compressible capacitance pinch sensor further has a non-conductive compressible element interposed between the first and second flexible conductor elements. The non-conductive compressible element compresses in response to an object within the opening touching the compressible capacitance pinch sensor such that the separation distance between the first and second flexible conductor elements decreases. The capacitance of the first and second flexible conductor elements changes in response to the separation distance between the first and second flexible conductor elements decreasing.
The pinch sensor system further includes a controller for monitoring the capacitance of the first and second flexible conductor elements. The controller determines the presence of the object within the opening in response to the capacitance of the first and second flexible conductor elements changing. The controller controls the closed opening device as a function of the change in capacitance.
Also, in carrying out the above objects and other objects, the present invention provides a seat occupant sensor system. The seat occupant sensor system includes at least one seat occupant sensor disposed within a seat. The at least one seat occupant sensor includes first, second, and third flexible conductor plates. The first flexible conductor plate is interposed between the second and third flexible conductor plates such that the first and third flexible conductor plates are separated by a separation distance. The second and third flexible conductor plates are electrically grounded and the first, second, and third flexible conductor plates have a capacitance dependent on the separation distance. The at least one seat occupant sensor further includes a first non-conductive compressible element interposed between the first and second flexible conductor plates and a second non-conductive compressible element interposed between the first and third flexible conductor plates. The first and second non-conductive compressible elements compress in response to a seat occupant applying force to the at least one seat occupant sensor such that the separation distance between the second and third flexible conductor plates decreases. The capacitance changes in response to the separation distance decreasing.
The seat occupant sensor system further includes a controller for determining characteristics of the seat occupant as a function of the capacitance of the at least one seat occupant sensor.
The at least one seat occupant sensor may include a seat back sensor disposed within a seat back of the seat. The controller determines whether the seat occupant is sitting back on the seat back as a function of the capacitance of the seat back sensor.
The at least one seat occupant sensor may include a seat bottom front sensor disposed within a front portion of a seat bottom of the seat. The controller determines whether the seat occupant is sitting short or forward on the seat bottom as a function of the capacitance of the seat bottom front sensor.
The at least one seat occupant sensor may include a seat bottom left sensor disposed within a left portion of a seat bottom of the seat and a seat bottom right sensor disposed within a right portion of the seat bottom. The controller determines whether the seat occupant is sitting left or right on the seat bottom as a function of the capacitances of the seat bottom left and right sensors.
The at least one seat occupant sensor may include at least one seat bottom sensor disposed within a seat bottom of the seat. The controller determines the weight of the seat occupant as a function of the capacitance of the at least one seat bottom sensor.
The controller may be operable to reverse the polarity between the first, second, and third flexible conductor plates such that the first conductor plate is electrically grounded. The controller monitors the capacitance of the at least one seat occupant sensor after reversing the polarity to determine whether the seat occupant is an animate or inanimate object.
The above objects and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the present invention when taken in connection with the accompanying drawings.